H3C S3600 Series Operating instructions

Brand: H3C

Model: S3600 Series

Type: Operating instructions

Operation Manual – DLDP

H3C S3600 Series Ethernet Switches-Release 1510 Table of Contents

Table of Contents

Chapter 1 DLDP Configuration ....................................................................................................1-1

1.1 DLDP Overview .................................................................................................................1-1

1.1.1 DLDP Fundamentals...............................................................................................1-2

1.1.2 Precautions during DLDP Configuration.................................................................1-6

1.2 DLDP Configuration...........................................................................................................1-7

1.2.1 DLDP Configuration Tasks......................................................................................1-7

1.2.2 Resetting DLDP State.............................................................................................1-9

1.3 DLDP Configuration Example............................................................................................1-9

Operation Manual – DLDP

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Chapter 1 DLDP Configuration

1.1 DLDP Overview

You may have encountered unidirectional links, namely, one-way audio, in networking.

When a unidirectional link occurs, the local device can receive packets from the peer

device through the link layer, but the peer device cannot receive packets from the local

device.

Unidirectional links can be divided into two types: one is caused by fiber

cross-connection, and the other is caused by a fiber being not connected or being

disconnected. The cross-connected fibers in

Figure 1-1 refer to optical fibers which are

connected inversely. The hollow lines in

Figure 1-2 refer to fibers which are not

connected or are broken.

Unidirectional links can cause many problems, such as spanning tree protocol (STP)

loop.

Device link detection protocol (DLDP) can detect the link status of an optical fiber cable

or copper twisted pair (such as super category 5 twisted pair). If DLDP finds a

unidirectional link, it disables the related port automatically or prompts you to disable it

manually according to the configurations, to avoid network problems.

SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

Figure 1-1 Fiber cross-connection

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SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

Figure 1-2 Fiber broken or not connecte

DLDP provides the following features:

z As a link layer protocol, it works together with the physical layer protocols to

monitor the link status of a device.

z The auto-negotiation mechanism at the physical layer detects physical signals and

faults. DLDP identifies peer devices and unidirectional links, and disables

unreachable ports.

z When auto-negotiation mechanism and DLDP are enabled, they work together to

detect and disable physical and logical unidirectional links, and to prevent the

failure of other protocols such as STP.

z Even if both ends of links can work normally at the physical layer, DLDP can detect

whether these links are connected correctly and whether packets can be

exchanged normally at both ends. However, the auto-negotiation mechanism

cannot implement this detection.

1.1.1 DLDP Fundamentals

I. DLDP status

A link can be in one of these DLDP states: initial, inactive, active, advertisement, probe,

disable, and delaydown.

Table 1-1 DLDP status

Status Description

Initial Initial status before DLDP is enabled.

Inactive DLDP is enabled but the corresponding link is down

Active DLDP is enabled, and the link is up or an neighbor entry is cleared

All neighbors communicate normally in both directions, or DLDP

remains in active state for more than five seconds and enters this

status. It is a stable state where no unidirectional link is found

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Status Description

Probe

DHCP sends packets to check whether the link is a unidirectional.

It enables the probe sending timer and an echo waiting timer for

each target neighbor.

Disable

DLDP detects a unidirectional link, or finds (in enhanced mode)

that a neighbor disappears. In this case, DLDP does not receive or

send DLDP packets.

Delaydown

When a device in the active, advertisement, or probe DLDP state

receives a port down message, it does not removes the

corresponding neighbor immediately, neither does it changes to

the inactive state. Instead, it changes to the delaydown state first.

When a device changes to the delaydown state, the related DLDP

neighbor information remains, and the Delaydown timer is

triggered.

II. DLDP timers

Table 1-2 DLDP timers

Timer Description

sending timer

Interval between sending advertisement packets, which can be

configured on a command line interface.

By default, the timer length is 10 seconds.

Probe sending

timer

The interval is 0.5 seconds. In the probe state, DLDP sends two

probe packets every second.

Echo waiting

timer

It is enabled when DLDP enters the probe state. The echo waiting

timer length is 10 seconds.

If no echo packet is received from the neighbor when the Echo

waiting timer expires, the state of the local end is set to

unidirectional link (one-way audio) and the state machine turns

into the disable state. DLDP outputs log and tracking information,

sends flush packets. Depending on the user-defined DLDP down

mode, DLDP disables the local port automatically or prompts you

to disable the port manually. At the same time, DLDP deletes the

neighbor entry.

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Timer Description

Entry aging

timer

When a new neighbor joins, a neighbor entry is created and the

corresponding entry aging timer is enabled

When an advertisement packet is received from a neighbor, the

neighbor entry is updated and the corresponding entry aging timer

is updated

In the normal mode, if no packet is received from the neighbor

when the entry aging timer expires, DLDP sends an advertisement

packet with an RSY tag, and deletes the neighbor entry.

In the enhanced mode, if no packet is received from the neighbor

when the entry aging timer expires, DLDP enables the enhanced

timer

The entry aging timer length is three times the advertisement timer

length.

Enhanced

timer

In the enhanced mode, if no packet is received from the neighbor

when the entry aging timer expires, DLDP enables the enhanced

timer for the neighbor. The enhanced timer length is 10 seconds

The enhanced timer then sends one probe packet every second

and eight packets successively to the neighbor.

If no echo packet is received from the neighbor when the

enhanced timer expires, the state of the local end is set to

unidirectional communication state and the state machine turns

into the disable state. DLDP outputs log and tracking information

and sends flush packets. Depending on the user-defined DLDP

down mode, DLDP disables the local port automatically or prompts

you to disable the port manually. Meanwhile, DLDP deletes the

neighbor entry.

Delaydown

timer

When a device in the active, advertisement, or probe DLDP state

receives a port down message, it does not removes the

corresponding neighbor immediately, neither does it changes to

the inactive state. Instead, it changes to the delaydown state first.

When a device changes to the delaydown state, the related DLDP

neighbor information remains, and the Delaydown timer is

triggered. The Delaydown timer is configurable and ranges from 1

to 5 seconds.

A device in the delaydown state only responds to port up

messages.

A device in the delaydown state resumes its original DLDP state if

it receives a port up message before the delaydown timer expires.

Otherwise, it removes the DLDP neighbor information and

changes to the inactive state.

III. DLDP operating mode

DLDP can operate in two modes: normal and enhanced.

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Table 1-3 DLDP operating mode and neighbor entry aging

DLDP

operating

mode

DLDP detects

whether

neighbors exist

or not when

neighbor tables

are aging

The entry aging timer

is enabled or not

during neighbor entry

aging

The enhanced

timer is enabled or

not when the entry

aging timer expires

Normal

mode

Yes (The neighbor

entry ages out after the

entry aging timer

expires)

Enhanced

mode

Yes

Yes (The enhanced

timer is enabled after

the entry aging timer

expires)

Yes (When the

enhanced timer

expires, the state of

the local end is set to

unidirectional link,

and the neighbor

entry is aged out.)

IV. DLDP implementation

1) If the DLDP-enabled link is up, DLDP sends DLDP packets to the peer device, and

analyzes and processes the DLDP packets received from the peer device. DLDP

in different states sends different types of packets.

Table 1-4 Types of packets sent by DLDP

DLDP state Packet type

Active

Advertisement packets, including those with or without an RSY

tag

Advertisement Advertisement packets

Probe Probe packets

2) DLDP analyzes and processes received packets from the peer device as follows:

z In authentication mode, DLDP authenticates the packets, and discards those

failing to pass the authentication.

z DLDP processes the received DLDP packets.

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Table 1-5 Process received DLDP packets

Packet type Processing procedure

If this neighbor entry does not exist on the

local device, DLDP creates the neighbor entry,

enables the entry aging timer, and switches to

the probe state.

packet

Extracts

neighbor

information

If the neighbor entry already exists on the local

device, DLDP updates the entry aging timer.

Flush packet Deletes the neighbor entry from the local device

Creates the neighbor entry if this neighbor

entry does not exist on the local device.

Probe packet

Sends echo

packets

containing both

neighbor and its

own information

to the peer

If the neighbor entry already exists on the local

device, updates the entry aging timer.

No Discards this echo packet

Sets the neighbor flag bit

to bidirectional link

Echo packet

Checks

whether

the local

device is

in the

probe

state

Yes

Checks

whether

neighbor

information

in the

packet is

the same

as that on

the local

device

Yes

If all neighbors are in the

bidirectional link state,

DLDP switches from the

probe state to the

advertisement state, and

sets the echo waiting

timer to 0.

3) If no echo packet is received from the neighbor, DLDP performs the following

processing:

Table 1-6 Processing procedure when no echo packet is received from the neighbor

No echo packet received

from the neighbor

Processing procedure

In normal mode, no echo

packet is received when the

echo waiting timer expires.

In enhanced mode, no echo

packet is received when the

enhanced timer expires

DLDP switches to the disable state, outputs log and

tracking information, and sends flush packets.

Depending on the user-defined DLDP down mode,

DLDP disables the local port automatically or

prompts you to disable the port manually. DLDP

sends an RSY message and deletes the neighbor

entry.

1.1.2 Precautions during DLDP Configuration

z DLDP works only when the link is up.

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z To ensure unidirectional links can be detected, you must make sure that DLDP is

enabled on both sides, and that the interval between sending advertisement

packets, authentication mode, and password are consistent on both sides.

z You can adjust the interval between sending advertisement packets in different

network circumstances so that DLDP can respond rapidly to a link failure. The

interval must be shorter than one-third of the STP convergence time, which is

generally 30 seconds. If too long an interval is set, an STP loop may occur before

DLDP shuts down unidirectional links. On the contrary, if too short an interval is set,

network traffic increases, and port bandwidth is reduced.

z DLDP does not process any LACP event, and treats each link in the aggregation

group as independent.

z When connecting two DLDP-enabled devices, make sure the software running on

them is of the same version. Otherwise, DLDP may operate improperly.

1.2 DLDP Configuration

1.2.1 DLDP Configuration Tasks

Table 1-7 DLDP configuration tasks

Operation Command Description

Enter system view

system-view

—

Enable DLDP

globally

dldp enable

Enter

Ethernet

port view

interface interface-type

interface-number

Enable

DLDP

Enable

DLDP

on a

port

Enable

DLDP on

a port

dldp enable

Required.

By default,

DLDP is

disabled.

Set the authentication mode and

password

dldp authentication-mode

{ none | simple

simple-password | md5

md5-password }

Optional.

By default, the

authentication

mode is none.

Set the interval of sending DLDP

packets

dldp interval timer-value

Optional.

By default, the

interval is 10

seconds.

Set the delaydown timer

dldp delaydown-timer

delaydown-time

Optional

By default, the

delaydown

timer expires

after 1 second

it is triggered.

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Operation Command Description

Set the DLDP handling mode

when an unidirectional link is

detected

dldp

unidirectional-shutdown

{ auto | manual }

Optional.

By default, the

handling mode

is auto.

Set the DLDP operating mode

dldp work-mode { enhance

| normal }

Optional.

By default,

DLDP works in

normal mode

and does not

detect

unidirectional

links.

Enter Ethernet port view

interface interface-type

interface-number

—

Force the duplex attribute

duplex full

Required

Force the speed value

speed speed-value

Required

Display the configuration

information about the

DLDP-enabled port

display dldp { unit-id |

interface-type

interface-number }

You can

execute this

command in

any view.

 Note:

z When you use the dldp enable/dldp disable command in system view to

enable/disable DLDP on all optical ports of the switch, the configuration takes effect

on the existing optical ports, instead of those added subsequently.

z DLDP can operate normally only when the same authentication mode and

password are set on the local and peer ports.

z When the DLDP protocol works in the normal mode, the system can identify only

one type of unidirectional link caused by fiber cross-connection.

z When the DLDP protocol works in enhanced mode, the system can identify two

types of unidirectional links: one is caused by fiber cross-connection and the other is

caused by one fiber being not connected or being broken.

z When the device is busy with services and the CPU utilization is high, DLDP may

issue mistaken reports. You are recommended to configure the operating mode of

DLDP as manual after unidirectional links are detected, so as to reduce the

influence of mistaken reports.

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1.2.2 Resetting DLDP State

 Note:

After a port is down due to the detection of unidirectional link, you can use the dldp

reset command to restore the DLDP state to perform DLDP detection.

Table 1-8 Reset DLDP state

Operation Command Description

Enter system view

system-view

—

Reset the DLDP state of the

system

dldp reset

Optional

Enter Ethernet port view

interface interface-type

interface-number

—

Reset the DLDP state of a port

dldp reset

Optional

Caution:

The dldp reset command only applies to the ports in the DLDP down state.

1.3 DLDP Configuration Example

I. Network requirements

As shown in Figure 1-3,

z Switch A and Switch B are connected through two pairs of fibers. Both of them

support DLDP.

z Suppose the fibers between Switch A and Switch B are connected inversely.

DLDP disconnects a unidirectional link after detecting it.

z When the network administrator connects the fiber correctly, the port shut down by

DLDP is restored.

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II. Network diagram

SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

SwitchB

SwitchA

GE2/1/3

GE2/1/4

Figure 1-3 Fiber cross-connection

III. Configuration procedure

1) Configure Switch A

# Configure the ports to work in mandatory full duplex mode at a rate of 1000 Mbps.

<H3CA> system-view

[H3CA] interface gigabitethernet 2/1/3

[H3CA-GigabitEthernet2/1/3] duplex full

[H3CA-GigabitEthernet2/1/3] speed 1000

[H3CA-GigabitEthernet2/1/3] quit

[H3CA] interface gigabitethernet 2/1/4

[H3CA-GigabitEthernet2/1/4] duplex full

[H3CA-GigabitEthernet2/1/4] speed 1000

[H3CA-GigabitEthernet2/1/4] quit

# Enable DLDP globally

[H3CA] dldp enable

# Set the interval between sending DLDP packets to 15 seconds.

[H3CA] dldp interval 15

# Configure DLDP to work in enhanced mode

[H3CA] dldp work-mode enhance

# Set the DLDP handling mode for unidirectional links to auto.

[H3CA] dldp unidirectional-shutdown auto

# Display the DLDP state

[H3CA] display dldp 1

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 Note:

When two switches are connected through fibers in a crossed way, two or three ports

may be in the disable state, and the rest in the inactive state.

When a fiber is connected to a device correctly on one end with the other end

connected to no device:

z If the device operates in the normal DLDP mode, the end that receives optical

signals is in the advertisement state; the other end is in the inactive state.

z If the device operates in the enhance DLDP mode, the end that receives optical

signals is in the disable state; the other end is in the inactive state.

# Restore the ports taken down by DLDP

[H3CA] dldp reset

2) Configure Switch B

The configuration of Switch B is the same to that of Switch A.

 Note:

z In order for DLDP to detect fiber disconnection in one direction, you must configure

the port to work in mandatory full duplex mode at a mandatory rate.

z When the port works in non-mandatory full duplex mode at a non-mandatory rate,

even if DLDP is enabled, it does not take effect when the fiber in one direction is

disconnected. In that case, the port is down.

H3C S3600 Series Operating instructions

H3C S3600 Series Operating instructions

H3C S3600 Series Operating instructions

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